document version compatibility policy (#41)

README.md

@@ -4,6 +4,11 @@ This is documentation for the [quic-go.net](https://quic-go.net), the documentat
 * [quic-go](https://github.com/quic-go/quic-go) (both the QUIC and HTTP/3 layer)
 * [webtransport-go](https://github.com/quic-go/webtransport-go)
 
+## Version Compatibility
+
+This documentation is focused **exclusively** on the most recent releases of quic-go and webtransport-go.
+No effort is made to document older versions.
+
 ## Running locally
 
 This site uses [Hugo](https://gohugo.io/). You can start a local webserver by running: